1. Field of the Invention
This invention relates to a method and associated apparatus for remote energizing of power storage devices and particularly to a method employing small apparatus for remote energizing of power storage devices using RF. The method of this invention preferably employs at least one antenna that has an effective area greater than its physical area to harvest energy.
2. Description of the Prior Art
Contactless electrical connections are well known in the field of portable electrical devices. For example, portable motorized toothbrushes typically contain a rechargeable battery, which is charged by induction. The inductive charging device is also called an electromagnetic, non-contact type battery charging device. The inductive charging device is advantageous in that it cannot be hindered by a bad electrical contact unlike the charging device that requires an electrical connection. Inductive charging devices typically consist of inductive coupler for transferring energy from a primary side of the inductive coupler on a charging device to a secondary side of the inductive coupler on the electronic device. Examples of inventions utilizing inductive charging include U.S. Pat. No. 6,284,651, U.S. Pat. No. 6,310,465 and U.S. Pat. No. 5,952,814. A major problem with inductive charging is that the charging device needs to be in close proximity to the electronic device in order to energized power storage devices in the electronic device.
To overcome the problems associated with inductive charging, charging devices using RF electromagnetic field radiated into free space have been described. U.S. Pat. No. 6,127,799 describes a charge storage device that is charged by exposing the charge storage device to an RF electromagnetic field radiated into free space. The charge storage device includes one or more antennas disposed on the device and adapted to receive the radiated RF electromagnetic field. One or more rectifiers are connected to the antennas for rectifying the received RF electromagnetic field into a DC output current. The DC output current produced by the rectifier is used to energize the charge storage device.
As disclosed in U.S. Pat. No. 6,127,799, the antennas may be one or more dipole antennas which are combined to form at least two subsets of dipole antenna element arrays, wherein one subset may be oriented at an acute or a right angle with respect to at least one other subset. The antennas or dipole antennas may be placed on more than one outside surface of the charge storage device, which enclose an acute or a right angle with respect to each other. The use of RF energy and antennae to develop remote charging using the technology disclosed in U.S. Pat. No. 6,127,799 has a shortcoming in that the power conversion efficiency of the antenna array in the disclosed invention is dependent on the number of dipoles. Also, the size of the dipole antennas for the device do not make it practical for the majority of portable electronic devices (e.g., cellular telephones, portable electronic games, digital camera's and the like). In this prior disclosure, the dipole antennas are used to cover more than one side of a battery that has a width of 12.5 cm.
An approach to overcoming the problems of prior art is through the use of antennas formed on electronic chips. Examples of prior art that disclose on-chip antennas include U.S. Pat. No. 4,857,893 (Carroll) and U.S. Pat. No. 6,373,447 (Rostoker).
The preferred approach as disclosed in U.S. Pat. No. 4,857,893 is to use a deposition technique that effectively creates a single monolithic chip assembly that includes all of the circuitry necessary to produce a functionally complete transponder unit. This patent discusses the use of magnetic film inductors on the chip to allow a reduction in the number of turns, and thereby make the fabrication of such inductors feasible. This patent references Soohoo, “Magnetic Thin Film Inductors For Integrated Circuit Applications”, IEEE Transactions in Magnetic, Vol. MAG-15, No. 6, pp. 1803-1805 (November 1979) and Salch and Qureshi, “Permalloy ThinFilm Inductors”, Electronic Letters, Vol. 6, No. 26, pp. 850-852 (Dec. 31, 1970). This patent discusses the construction of the antenna on a chip as follows: A 10-turn square spiral coil for use at 10 MHz is constructed having an outer diameter of 1 cm×1 cm. The conducting path width is 0.005 inches. The spacing between turns is 0.001 in. The copper path is deposited by vacuum evaporation and then thickness is built up to about 25 micrometers by electroplating. Two permalloy magnetic films, having a thickness of from 1000-3000 Angstroms, surround the conductors, one on top, and the other on the bottom. The film is evaporated in an orienting magnetic field in such a way that the long dimension is parallel to the field and, therefore, is the easy direction of magnetization of the film. When a high-frequency current passes in the coil, the magnetic films are driven in a hard direction, and the two magnetic films around each conductor act as a magnetic core enclosing a 1-turn coil. The effect of the magnetic films is to increase the inductance of the coil in addition to its free-space inductance. The magnetic permeability is quite large, as the films are driven in the hard direction. Further, an insulating silicon-monoxide layer (SiO, 10,000 A thick) separates each magnetic film from the conducting path.
The problem with the approach as disclosed by Carroll U.S. Pat. No. 4,857,893 is the need to deposit a permalloy magnetic film, or other suitable material having a large magnetic permeability and electrical insulating properties in order increase the inductance of the coil. This increases the cost and complexity of the antenna of a chip. It also limits the ability to shrink the size of the antenna because of the need for magnetic film layers between the antenna coil(s).
U.S. Pat. No. 6,373,447 (Rostoker) discloses the use of one or more antennas that are formed on an integrated circuit (IC) chip and connected to other circuitry on the IC chip. Antenna configurations are disclosed that include loop, multi-turn loop, square spiral, long wire, or dipole. The antenna as disclosed could be formed to have two or more segments, which can selectively be connected to one another to alter an effective length of the antenna. Furthermore, two antennas may be formed in two different metallization layers separated by an insulating layer. A major shortcoming of this prior art is that the inventors teach that the antenna's transmitting and receiving strength “is proportional to the number of turns and area of the loop.”
There remains a need for small remote power charger device and associated method that have a means for receipt of transmitted energy from the environment and energizing power storage devices on an object of interest wherein the power charger device is not dependent on inductive charging.
There is also a need for a small remote power charger device and associated method having a means for receipt of transmitted energy from the environment and energizing power storage devices on an object of interest using one or more antenna(e) on a substrate.
Finally, there is a need for a small remote power charger device and associated method that uses one or more antenna(e) on a substrate wherein the strength of the antenna is not dependent on magnetic induction or number of turns and area of the loop of the antenna.